What was once among Southcentral Alaska's most popular spring and summer recreation activities may soon be in danger of being forgotten.

Clamming on several Kenai Peninsula beaches on the eastern shore of Cook Inlet will be closed yet again in 2017 — closures that date to 2014 — due to a collapsing razor clam population, the Alaska Department of Fish and Game announced on Wednesday. Beaches from the mouth of the Kenai River south to the Homer Spit will be shuttered to the taking of all clams.

The five beaches are Clam Gulch north and south, Ninilchik north and south, and another beach between Clam Gulch and Ninilchik.

Those same beaches used to be mobbed with diggers toting shovels or clam guns who would bring home dozens of clams on successful outings. The peak year was 1994, when Fish and Game estimated the harvest at 1.3 million clams during 48,000 "digger days" — a clam-digger spending at least part of a day on the beach.

Since 2015 — zilch.

But state biologists suggest that the clam population may be starting to rebuild itself.

While surveys conducted earlier this year found almost no mature (at least 3 1/4 inches long) clams, they did detect lots of juveniles — some 2.5 million in the northern section of the Clam Gulch beach.

That "signals that the population may be beginning to rebound," noted Carol Kerkvliet, a Homer-based fisheries biologist with the Alaska Department of Fish and Game. And that amounts to a turnaround from 2015, when juvenile clams were "still at historic low levels, lower than ever," she said at the time.

What caused the crash remains a mystery. So is whether there is any connection between the clam crash and recent die-offs of sea stars, otters and murres in Kachemak Bay.

"That's the question we're all trying to answer," said Kris Holderied, oceanographer with the National Oceanic and Atmospheric Administration.

"The last two winters, we never had the big cold-air outbreak, cooling the northern Gulf of Alaska. It rained all winter long and that freshwater stabilized the water column. Not only are you not cooling it but it stops nutrients from mixing and changes what happens with the plankton."

Blooms of a plankton called Alexandrium, associated with warm water, burst into Kachemak Bay, resulting in the first high levels of paralytic shellfish poisoning toxins recorded in more than a decade.

Kerkvliet said the clam crash "is thought to have resulted from a combination of poor spawning and high natural mortality of mature-size razor clams.

"In terms of what is causing the problem, we don't have a silver bullet. There was no harvest on those beaches in the past two years, so that would seem to point to some environmental factor or factors."

Razor clams' lifespan can stretch to at least 18 years and some don't become sexually mature until their seventh growing season. Fertilization occurs by chance, with eggs and sperm discharged into sand and swirling water, but the number of eggs a single female can produce is mind-boggling — up to 118 million, according to Fish and Game.

Eventually, they can grow to 7 inches long; they should be at least 3 1/4 inches long to be what are termed "exploitable" clams, and Alaskans once were allowed to take home 60 a day from Kenai beaches. As the population crashed, limits were reduced and, before long, eliminated.

"It's too early to say" whether the young clams on Kenai Peninsula beaches will be big enough to harvest in 2018, permitting the season to reopen, said Matt Miller, Southcentral regional fisheries management coordinator with Fish and Game. "It takes about three years before clams get big enough."

The clamming closure removes one of the few harvesting prospects available to Alaskans before salmon begin returning to Alaska waterways around Memorial Day.

"It was a big thing in the spring, the first thing that really happened," Miller said. "People would find that big low tide and go harvest some clams."